The present invention relates to a cryosurgical instrument and, more particularly to a liquid nitrogen spray apparatus that can be used in treating lesions, benign or malignant, that respond to cryosurgery.
In the medical practice there have been various types of spraying apparatus used in cryosurgery for the treatment of skin lesions. Using layman's terms, the skin lesions may be any type of definite growth in the skin (warts being an example) or an infection in the skin (acne be an example). In recent years, cryosurgery has been used to treat cancerous or malignant tumors in the skin. The cancerous areas may be located on either the internal areas of the body or on the exterior skin.
Regardless of the type of cryosurgical instrument that is used, the lesion must be frozen to at least -20.degree. C. to insure the destruction of all the abnormal cells. Though, various types of liquefied gas coolants may be used in cryosurgical instruments, the usual liquefied gas used by the medical profession is liquid nitrogen which has a boiling point of -196.degree. C. Because of the extremely low temperature of the liquid nitrogen, it must be stored in special containers to prevent evaporation into the atmosphere. Also, if any moving parts come into contact with the liquid nitrogen, they may freeze up or stick due to a moisture collection from the atmosphere. Any flexible hosing that may come in contact with the liquid nitrogen becomes very rigid and brittle. Many early cryosurgical instruments, such as the one shown in U.S. Pat. No. 3,739,956, issued to Reynolds, used various types of valving apparatus and moving parts which came into contact with the liquid refrigerant. Due to the extreme cold, all the valving apparatus would freeze up in a very short period of time causing the liquid coolant to rapidly evaporate into the atmosphere. Those cryosurgical instruments were not only wasteful of the liquefied gas but were also fairly complex and expensive to manufacture.
Another common apparatus, such as the ones shown in U.S. Pat. Nos. 3,534,739 and 3,651,813, contained no moving parts in contact with the liquefied gas coolant. However, those instruments were closed systems which caused the coolant to continuously boil inside the container and completely evaporate in a very short period of time. When normal venting is stopped, pressure built up in the container causes a stream of coolant to be ejected from the nozzle. In a single operation of thirty minutes or more, the container would have to be filled repeatedly because many operations require numerous treatments of the lesions by the liquid gas coolant to insure its complete destruction. Although the above apparatus' are inexpensive to manufacture, they are extremely wasteful of liquid coolant as well as being impossible to use for repeated time interval treatments without coolant refills.
A third type of cryosurgical instrument, such as the TT-32 Liquid Nitrogen Sprayer, by Physicians Products, Inc., Box 44, Millbrae, Calif. 94030, used vacuum bottles to avoid coolant waste and further contained a valving mechanism to allow normal venting of pressure built in the vacuum bottle. That normal venting would dissipate the pressure sufficiently so that there would be no continuous ejection of liquid coolant from the nozzle. To facilitate operation, these instruments were provided with a squeeze bulb to increase the pressure in the vacuum bottle once the valving mechanism was closed. Unfortunately, these systems were designed with the valve mechanism being of a screw type and being situated immediately above the squeeze bulb. That configuration made the instrument inconvenient to operate and in many instances required two people to insure proper use. Furthermore, after squeezing the squeeze bulb with the valve closed, liquid nitrogen is ejected from the nozzle and will continue to eject until the pressure inside the vacuum bottle has been dissipated. That may result in an excess of the liquid coolant reaching the skin lesion or adjacent normal areas with resultant damage to skin tissue. Because the valve is a screw type valve, it is not easy to rapidly open and close resulting in a loss of the delicate control of the amount of coolant delivered which is so highly desirable in such a unit especially in treating very sensitive areas about the eyes, face, genitalia, etc. Although these instruments are inexpensive and do not waste liquid nitrogen as long as the vent valve remains open, there use under hospital conditions is very awkward and inconvenient.
To overcome the above problems, a cryosurgical spraying apparatus, disclosed in U.S. Pat. No. 3,889,681, issued to the inventor of the present application and herein incorporated by reference, was produced with a continuous open vent provided immediately above the squeeze bulb which may be closed by placing the thumb over the opening. When the thumb is removed from the opening, the pressure inside the vacuum bottle immediately decreases to stop the ejection of the liquid coolant. That venting mechanism provides an extremely delicate and precise control of the amount of coolant delivered. Although that system is far superior to any of the preceding systems, it too is in many instances awkward and inconvenient to use as well as more expensive to manufacture than the present invention.
The position of the open vent directly above the squeeze bulb makes it difficult to pump the bulb to initiate a steady stream of liquid coolant while still maintaining the vent closed with the thumb of that hand.
Therefore, the design, as embodied in the present invention, has been improved by moving the vent to a position on the cap directly below the nozzle. That position allows a user to securely hold the instrument with one hand and use a index finger of that hand to cover and uncover the vent. Thus, the opposite hand is freed to squeeze the bulb as needed or provide some other necessary medical movement or operation. It further prevents an excess of liquid coolant from being applied to the skin lesion because of the extremely precise and delicate control made possible by the finger control venting. The present invention also incorporates a standard Leur lock-head for the rapid and easy attachment of tips (needles) of any diameter and length necessary to treat lesions of any size and location.